Integrator input error correction circuit and circuit method

Abstract

A circuit includes a first amplifier and a second amplifier, wherein first amplifier is configured to receive an input current at a first input of the first amplifier, and an output of the first op-mp is configured to drive a first input of the second amplifier. The circuit further includes a pull-up current source selectively coupled to the first input of the second amplifier, and a pull-down current source selectively coupled to the first input of the second amplifier. If the absolute value of the input current is larger than a predefined threshold current: i) the pull-up current source is configured to drive current into the first input of the second amplifier for a first polarity of the input current, and ii) the pull-down current source is configured to sink current from the first input of the second amplifier for a second polarity of the input current.

What is claimed is: 
     
       1. A circuit comprising:
 a first amplifier configured to receive an input current at a first input of the first amplifier, an output of the first amplifier being configured to drive a first input of a second amplifier; and 
 one or more current sources selectively coupled to the first input of the second amplifier, wherein if a value of the input current is larger than a predefined threshold, the one or more current sources are configured to drive current into the first input of the second amplifier for a first polarity of the input current, and sink current from the first input of the second amplifier for a second polarity of the input current. 
 
     
     
       2. The circuit of  claim 1 , wherein the value of the input current is an absolute value of the input current. 
     
     
       3. The circuit of  claim 1 , wherein the one or more current sources includes a pull-up current source that is configured to be selectively coupled to the first input of the second amplifier if the input current has the first polarity. 
     
     
       4. The circuit of  claim 1 , wherein the one or more current sources includes a pull-down current source that is configured to be selectively coupled to the input of the second amplifier if the input current has the second polarity. 
     
     
       5. The circuit of  claim 1 , further comprising at least one switch coupled between the one or more current sources and the first input of the second amplifier, wherein the at least one switch is configured to be controlled by at least one control signal to selectively couple and de-couple the one or more current sources to and from the first input of the second amplifier. 
     
     
       6. The circuit of  claim 1 , further comprising a signal generator configured to:
 receive a digital signal; 
 generate the input current, wherein the input current is a pulse width modulated (PWM) current signal that encodes the digital signal; and 
 generate at least one control signal based on the PWM current signal, wherein the at least one control signal is used to selectively couple and de-couple the one or more current sources to and from the first input of the second amplifier. 
 
     
     
       7. The circuit of  claim 1 , further comprising an output stage configured to generate an output signal for driving a load based on a set of control signals, wherein the set of control signals includes timing information for controlling a timing of the output signal. 
     
     
       8. The circuit of  claim 1 , further comprising an output stage configured to generate at least one control signal for controlling at least one switch based on a timing of a set of control signals, wherein the at least one switch is used to selectively couple and de-couple the one or more current sources to and from the first input of the second amplifier. 
     
     
       9. The circuit of  claim 1 , further comprising a feedback path between an output of an output stage and the first input of the first amplifier, the feedback path including a resistor for converting voltages of an output signal to a feedback current, wherein:
 the feedback current causes a non-zero input voltage across the first input of the first amplifier and a second input of the first amplifier, and 
 the one or more current sources are configured to pull current from or drive current into the first input of the second amplifier to force a zero input voltage across the first input of the second amplifier and a second input of the second amplifier. 
 
     
     
       10. The circuit of  claim 1 , wherein the first amplifier, second amplifier, and one or more current sources are in an integrator that is configured to integrate the input current, and the drive current and the sink current are a function of a compensation capacitance and an integration capacitance of the integrator. 
     
     
       11. A method comprising:
 receiving an input current at a first amplifier; 
 driving a first input of a second amplifier with an output of the first amplifier; and 
 when a value of the input current is larger than a predefined threshold, using one or more current sources to drive current into the first input of the second amplifier for a first polarity of the input current and to sink current from the first input of the second amplifier for a second polarity of the input current. 
 
     
     
       12. The method of  claim 11 , wherein the value of the input current is an absolute value of the input current. 
     
     
       13. The method of  claim 11 , wherein the one or more current sources includes a pull-up current source, the method further comprising selectively coupling the pull-up current source to the first input of the second amplifier if the input current has the first polarity. 
     
     
       14. The method of  claim 11 , wherein the one or more current sources includes a pull-down current source, the method further comprising selectively coupling the pull-down current source to the input of the second amplifier if the input current has the second polarity. 
     
     
       15. The method of  claim 11 , further comprising using at least one control signal to control at least one switch coupled between the one or more current sources and the first input of the second amplifier. 
     
     
       16. The method of  claim 11 , further comprising:
 receiving a digital signal; 
 generating the input current, wherein the input current is a pulse width modulated (PWM) current signal that encodes the digital signal; 
 generating at least one control signal based on the PWM current signal; and 
 using the at least one control signal to selectively couple and de-couple the one or more current sources to and from the first input of the second amplifier. 
 
     
     
       17. The method of  claim 11 , further comprising generating an output signal for driving a load based on a set of control signals, wherein the set of control signals includes timing information for controlling a timing of the output signal. 
     
     
       18. The method of  claim 11 , further comprising:
 generating at least one control signal for controlling at least one switch based on a timing of a set of control signals; and 
 using at least one switch to selectively couple and de-couple the one or more current sources to and from the first input of the second amplifier. 
 
     
     
       19. The method of  claim 11 , further comprising:
 providing a feedback current over a feedback path between an output of an output stage and the first input of the first amplifier, the feedback path including a resistor for converting voltages of an output signal to the feedback current, wherein the feedback current causes a non-zero input voltage across the first input of the first amplifier and a second input of the first amplifier, and 
 forcing a zero input voltage across the first input of the second amplifier and a second input of the second amplifier by using the one or more current sources to pull current from or drive current into the first input of the second amplifier. 
 
     
     
       20. The method of  claim 11 , wherein the first amplifier, second amplifier, and one or more current sources are in an integrator that is configured to integrate the input current, and the drive current and the sink current are a function of a compensation capacitance and an integration capacitance of the integrator.